I've decided to take on the task of fixing/replacing the head gasket myself

I need some advice as I am down to the last part, removing the heads. I'm trying to ease out the head but the piston casing seems to be coming out with it. Are they connected or can I remove the head without the piston coming out?
I've looked on wiki but can't find anything and the haynes manual does not give any info, or if it does I can't find it.
Cheers guys
Ben